1. Field
The invention is in the field of treating and stabilizing buried waste, areas of contaminated earth or soil, sludge lagoons, or similar types of materials.
2. State of the Art
In many cases, waste is disposed of by burying the waste. In some cases, particularly in the disposal of radioactive wastes, shallow trenches are dug about three meters wide and between three and five meters deep and waste is deposited in such trenches. When filled with waste to about one meter of the top of the trench, the trench is covered with earth to cover the waste. Such waste presents a huge volume of heterogeneous contamination which is continually percolating into the soil and ground water. The buried waste usually includes various types of containers such as plastic bags, cardboard boxes, steel drums, and glass containers. The useful life of these containers to act as localized containment is usually much less than the time over which the enclosed chemicals or other wastes remain dangerous and can inflict harm to the environment.
It has become desirable for various buried waste sites to stabilize the waste in some way. This may be done by injecting stabilizing fluids into the buried waste. In many cases a grout is injected under relatively low pressure into the waste material with the expectation that the grout will flow through the waste, surround it, and solidify to stabilize such waste. With normal low pressure grouting procedures, however, the grout does not generally penetrate the various containers of waste, but merely surrounds them with grout. It has been found that by merely surrounding the containers with grout, the containers remain unstabilized and can collapse over time, thus creating voids in the mass of grout and waste formed by the low pressure grout treatment. The unstabilized waste, if mobile, can migrate through the open void spaces in the grout and be released and the voids created can lead to subsidence or collapse of the skeletal structure of the solidified grout.
The limitations of conventional low pressure grout injection can be overcome using high velocity jets to cut and mix the waste with stabilizing agents. However, conventional jet injection requires the use of surface drilling equipment to install the injection lances and to pull the lances from the ground during injection. Usually, a single drill hole is injected over its entire length, starting at the bottom of the hole and moving upwardly toward the top. When injection is completed for one hole, the drilling equipment is then moved to the next hole and the process is repeated. When stabilizing contaminated waste in this manner, several problems arise:
a) Because the buried waste includes open void space, grout tends to flow away from the area immediately surrounding the hole being injected. This grout flow is similar to low pressure conventional grouting which cannot form a homogeneous stabilized waste form due to the presence of intact containers.
b) The flow of grout outside the area immediately surrounding the hole being injected, i.e., outside the zone of influence of the cutting jet, increases the depth of grout inside the buried waste and inside adjacent untreated holes. As more drill holes are injected, the grout depth increases inside the buried waste and in remaining untreated drill holes. As injection lances are inserted into these untreated holes, they become submerged in the grout filling these holes. The submergence of the lances and thus the jets of grout emanating therefrom causes a severe loss of cutting energy of the jets. If the grout in an untreated hole has hardened before the lance is inserted, all benefits of the high pressure jet is lost.
c) Conventional jet injection usually requires the use of a surface drill to rotate and extract the injection lances. Rotation of the lances is necessary to direct the jet in various directions around the hole. The rotation, however, does not allow the cutting energy to be projected as far as when the jets are directed in a single direction as they are lifted. The rotating lances do not have enough concentrated cutting energy to cut robust containers, such as steel drums or wooden boxes.
d) Due to the necessary rotation of the jets, the only way to ensure cutting of robust containers is to rupture the containers during the installation of the injection lance. This requires very close spacing between injection holes, typically 50-75 cm.
e) Since a surface drill is used to rotate and extract the injection lances and the injection holes are sequentially injected from bottom to top, there is a very high probability that the surface mounted drill and operators can become exposed to contaminated waste which is ejected from the ground. Alternatively, the stabilizing fluid may break out of the ground and erupt at the surface increasing the likelihood of worker and equipment exposure to contamination.